A number of medical conditions can produce a loss of nerve sensation in the extremities such as the hands and feet of normally active persons. These include, among others, diabetes, nerve injury, spina bifada, Hansen's disease, syringomyelia and peripheral neuritis. In many cases the most easily noted locale of such insensitivity or loss of nerve sensation occurs in one or both feet of an individual. When such insensitivity occurs the normal sensations of discomfort or pain are not present and the individual can incur damage to the soft tissues of the foot due to prolonged pressure, rubbing, or other condition caused by walking, standing or other movement, particularly in tight or ill-fitting shoes. This damage to the feet is particularly prevalent in persons who have developed diabetes, but are still normally active individuals and if not treated early can result in rupturing of the skin or ulceration of the soft tissues of the foot.
Other persons can also incur abnormal pressures on the tissues of the feet as a result of a variety of conditions, such as prolonged standing or walking, job stresses, deformations of the arches of the feet, birth defects and traumatic injuries.
A variety of treatments for the prevention of such conditions have been developed which vary in their effectiveness. The more successful have involved additions to or redesign of footwear for use by persons with such insensitivity of or abnormal pressures on the feet. Added soft padding, and particularly, energy-absorbing insoles are most frequently used. In addition, some added modifications to the soles of shoes have been suggested, such as, metatarsal bars, rocker bars or wedges and, in case of deformed feet or extreme pressure conditions, alterations such as rocker soles or the like are prescribed. These latter alterations of the shoe are designed to co-exist with changes in the gait or stride of the person when walking. All of such expedients basically aim at reducing the concentration of pressure forces on areas of the plantar surface of the foot, and limiting the lift-off of the heel so less pressure is imposed on the forefoot.
Accordingly, the present invention is concerned with providing a shoe sole which provides for the redistribution and relief of excessive pressure conditions which frequently occur from walking or standing in daily activities or by persons with insensitive feet and particularly persons suffering from diabetes or one of the other conditions mentioned above. The present invention provides a sole structure for shoes which functions when walking in such a way as to reduce the total pressures imposed on the plantar surface of the forefoot and therefore to lessen the time such pressures are imposed on the metatarsal heads and on the plantar surfaces of the phalanges during walking. The present invention therefore represents a substantial improvement in shoe soles for active individuals and those with insensitive extremities and overcomes many of the disadvantages and shortcomings of previously known shoe soles intended for such purposes.